* High resolution timers on ACPI-less kernel
@ 2007-10-09 9:06 John Sigler
2007-10-09 9:15 ` Alessio Igor Bogani
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: John Sigler @ 2007-10-09 9:06 UTC (permalink / raw)
To: linux-rt-users, linux-acpi; +Cc: Thomas Gleixner
[-- Attachment #1: Type: text/plain, Size: 2161 bytes --]
Hello everyone,
I'm using a -rt kernel with high resolution timer support.
http://rt.wiki.kernel.org/index.php/Main_Page
Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT
RT Tue Oct 9 10:02:45 CEST 2007
I enabled high resolution timer support and disabled ACPI support.
CONFIG_TICK_ONESHOT=y
# CONFIG_NO_HZ is not set
CONFIG_HIGH_RES_TIMERS=y
CONFIG_GENERIC_CLOCKEVENTS_BUILD=y
# CONFIG_SMP is not set
...
CONFIG_PREEMPT_RT=y
CONFIG_PREEMPT=y
CONFIG_PREEMPT_SOFTIRQS=y
CONFIG_PREEMPT_HARDIRQS=y
CONFIG_PREEMPT_BKL=y
# CONFIG_CLASSIC_RCU is not set
CONFIG_PREEMPT_RCU=y
# CONFIG_RCU_TRACE is not set
CONFIG_X86_UP_APIC=y
CONFIG_X86_UP_IOAPIC=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_X86_IO_APIC=y
...
CONFIG_MTRR=y
CONFIG_REGPARM=y
# CONFIG_SECCOMP is not set
CONFIG_HZ_100=y
# CONFIG_HZ_250 is not set
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=100
High resolution timers do not work in this configuration.
Consider the following app where I request a 2 ms sleep
(where the time quantum is 10 ms).
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <sched.h>
static void set_SCHED_RR(int priority)
{
struct sched_param param = { 0 };
param.sched_priority = priority;
int err = sched_setscheduler(0, SCHED_RR, ¶m);
if (err) perror("sched_setscheduler");
}
int main(void)
{
struct timespec t0, t1, ms = { 0, 2000000 };
set_SCHED_RR(20);
while ( 1 )
{
clock_gettime(CLOCK_REALTIME, &t0);
nanosleep(&ms, NULL);
clock_gettime(CLOCK_REALTIME, &t1);
long diff = (t1.tv_sec-t0.tv_sec)*1000000000 + (t1.tv_nsec-t0.tv_nsec);
printf("delta = %ld\n", diff);
}
return 0;
}
# ./test
delta = 6026911
delta = 9926038
delta = 9989993
delta = 9995600
delta = 9993176
delta = 9994805
delta = 9994822
delta = 9994978
delta = 9994912
delta = 9994998
delta = 9994878
delta = 9994513
Any idea why?
# cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc pit jiffies
# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc
My timestamp counter is good. Why do I need ACPI for hrt?
I've attached dmesg output.
Regards.
[-- Attachment #2: dmesg.no.acpi.txt --]
[-- Type: text/plain, Size: 9540 bytes --]
Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT RT Tue Oct 9 10:02:45 CEST 2007
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 00000000000a0000 (usable)
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000000fef0000 (usable)
BIOS-e820: 000000000fef0000 - 000000000fef3000 (ACPI NVS)
BIOS-e820: 000000000fef3000 - 000000000ff00000 (ACPI data)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
254MB LOWMEM available.
found SMP MP-table at 000f4fa0
Entering add_active_range(0, 0, 65264) 0 entries of 256 used
Zone PFN ranges:
DMA 0 -> 4096
Normal 4096 -> 65264
early_node_map[1] active PFN ranges
0: 0 -> 65264
On node 0 totalpages: 65264
DMA zone: 32 pages used for memmap
DMA zone: 0 pages reserved
DMA zone: 4064 pages, LIFO batch:0
Normal zone: 477 pages used for memmap
Normal zone: 60691 pages, LIFO batch:15
DMI 2.2 present.
Intel MultiProcessor Specification v1.4
Virtual Wire compatibility mode.
OEM ID: OEM00000 Product ID: PROD00000000 APIC at: 0xFEE00000
Processor #0 15:2 APIC version 17
I/O APIC #2 Version 17 at 0xFEC00000.
Enabling APIC mode: Flat. Using 1 I/O APICs
Processors: 1
Allocating PCI resources starting at 10000000 (gap: 0ff00000:eed00000)
Real-Time Preemption Support (C) 2004-2007 Ingo Molnar
Built 1 zonelists. Total pages: 64755
Kernel command line: ro root=/dev/hdc1 console=ttyS0,57600n8 console=tty0 panic=3 apic=debug nmi_watchdog=0
mapped APIC to ffffd000 (fee00000)
mapped IOAPIC to ffffc000 (fec00000)
Enabling fast FPU save and restore... done.
Enabling unmasked SIMD FPU exception support... done.
Initializing CPU#0
WARNING: experimental RCU implementation.
PID hash table entries: 1024 (order: 10, 4096 bytes)
Detected 2400.000 MHz processor.
Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
Memory: 256308k/261056k available (1274k kernel code, 4252k reserved, 451k data, 128k init, 0k highmem)
virtual kernel memory layout:
fixmap : 0xfffbc000 - 0xfffff000 ( 268 kB)
vmalloc : 0xd0800000 - 0xfffba000 ( 759 MB)
lowmem : 0xc0000000 - 0xcfef0000 ( 254 MB)
.init : 0xc02b2000 - 0xc02d2000 ( 128 kB)
.data : 0xc023e9ef - 0xc02af92c ( 451 kB)
.text : 0xc0100000 - 0xc023e9ef (1274 kB)
Checking if this processor honours the WP bit even in supervisor mode... Ok.
Calibrating delay using timer specific routine.. 4802.76 BogoMIPS (lpj=24013820)
Mount-cache hash table entries: 512
CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 00004400 00000000 00000000
CPU: Trace cache: 12K uops, L1 D cache: 8K
CPU: L2 cache: 512K
CPU: After all inits, caps: bfebfbff 00000000 00000000 0000b080 00004400 00000000 00000000
Compat vDSO mapped to ffffe000.
CPU: Intel(R) Pentium(R) 4 CPU 2.40GHz stepping 09
Checking 'hlt' instruction... OK.
Getting VERSION: 50014
Getting VERSION: 50014
Getting ID: 0
Getting LVT0: 700
Getting LVT1: 400
enabled ExtINT on CPU#0
ExtINT not setup in hardware but reported by MP table
ENABLING IO-APIC IRQs
Setting 2 in the phys_id_present_map
...changing IO-APIC physical APIC ID to 2 ... ok.
init IO_APIC IRQs
IO-APIC (apicid-pin) 2-0, 2-5, 2-7, 2-9, 2-10, 2-11, 2-20, 2-21, 2-22 not connected.
..TIMER: vector=0x31 apic1=0 pin1=2 apic2=0 pin2=0
number of MP IRQ sources: 19.
number of IO-APIC #2 registers: 24.
testing the IO APIC.......................
IO APIC #2......
.... register #00: 02000000
....... : physical APIC id: 02
....... : Delivery Type: 0
....... : LTS : 0
.... register #01: 00178020
....... : max redirection entries: 0017
....... : PRQ implemented: 1
....... : IO APIC version: 0020
.... register #02: 00000000
....... : arbitration: 00
.... register #03: 00000001
....... : Boot DT : 1
.... IRQ redirection table:
NR Log Phy Mask Trig IRR Pol Stat Dest Deli Vect:
00 000 00 1 0 0 0 0 0 0 00
01 001 01 0 0 0 0 0 1 1 39
02 001 01 0 0 0 0 0 1 1 31
03 001 01 0 0 0 0 0 1 1 41
04 001 01 0 0 0 0 0 1 1 49
05 000 00 1 0 0 0 0 0 0 00
06 001 01 0 0 0 0 0 1 1 51
07 000 00 1 0 0 0 0 0 0 00
08 001 01 0 0 0 0 0 1 1 59
09 000 00 1 0 0 0 0 0 0 00
0a 000 00 1 0 0 0 0 0 0 00
0b 000 00 1 0 0 0 0 0 0 00
0c 001 01 0 0 0 0 0 1 1 61
0d 001 01 0 0 0 0 0 1 1 69
0e 001 01 0 0 0 0 0 1 1 71
0f 001 01 0 0 0 0 0 1 1 79
10 001 01 1 1 0 1 0 1 1 81
11 001 01 1 1 0 1 0 1 1 89
12 001 01 1 1 0 1 0 1 1 91
13 001 01 1 1 0 1 0 1 1 99
14 000 00 1 0 0 0 0 0 0 00
15 000 00 1 0 0 0 0 0 0 00
16 000 00 1 0 0 0 0 0 0 00
17 001 01 1 1 0 1 0 1 1 A1
IRQ to pin mappings:
IRQ0 -> 0:2
IRQ1 -> 0:1
IRQ3 -> 0:3
IRQ4 -> 0:4
IRQ6 -> 0:6
IRQ8 -> 0:8
IRQ12 -> 0:12
IRQ13 -> 0:13
IRQ14 -> 0:14
IRQ15 -> 0:15
IRQ16 -> 0:16
IRQ17 -> 0:17
IRQ18 -> 0:18
IRQ19 -> 0:19
IRQ23 -> 0:23
.................................... done.
Using local APIC timer interrupts.
calibrating APIC timer ...
... lapic delta = 833376
... PM timer delta = 0
..... delta 833376
..... mult: 35793226
..... calibration result: 1333401
..... CPU clock speed is 2400.1228 MHz.
..... host bus clock speed is 133.3401 MHz.
... verify APIC timer
... jiffies delta = 10
... jiffies result ok
NET: Registered protocol family 16
PCI: PCI BIOS revision 2.10 entry at 0xfb3e0, last bus=1
PCI: Using configuration type 1
Setting up standard PCI resources
PCI: Probing PCI hardware
PCI: Probing PCI hardware (bus 00)
PCI quirk: region 0400-047f claimed by ICH4 ACPI/GPIO/TCO
PCI quirk: region 0480-04bf claimed by ICH4 GPIO
PCI: Transparent bridge - 0000:00:1e.0
PCI: Using IRQ router PIIX/ICH [8086/24c0] at 0000:00:1f.0
querying PCI -> IRQ mapping bus:0, slot:2, pin:0.
PCI->APIC IRQ transform: 0000:00:02.0[A] -> IRQ 16
querying PCI -> IRQ mapping bus:0, slot:31, pin:0.
PCI->APIC IRQ transform: 0000:00:1f.1[A] -> IRQ 16
querying PCI -> IRQ mapping bus:0, slot:31, pin:1.
PCI->APIC IRQ transform: 0000:00:1f.3[B] -> IRQ 17
querying PCI -> IRQ mapping bus:1, slot:2, pin:0.
PCI->APIC IRQ transform: 0000:01:02.0[A] -> IRQ 16
querying PCI -> IRQ mapping bus:1, slot:3, pin:0.
PCI->APIC IRQ transform: 0000:01:03.0[A] -> IRQ 17
querying PCI -> IRQ mapping bus:1, slot:4, pin:0.
PCI->APIC IRQ transform: 0000:01:04.0[A] -> IRQ 18
querying PCI -> IRQ mapping bus:1, slot:5, pin:0.
PCI->APIC IRQ transform: 0000:01:05.0[A] -> IRQ 19
querying PCI -> IRQ mapping bus:1, slot:15, pin:0.
PCI->APIC IRQ transform: 0000:01:0f.0[A] -> IRQ 23
PCI: Bridge: 0000:00:1e.0
IO window: c000-cfff
MEM window: ec000000-edffffff
PREFETCH window: 10000000-100fffff
PCI: Setting latency timer of device 0000:00:1e.0 to 64
NET: Registered protocol family 2
IP route cache hash table entries: 2048 (order: 1, 8192 bytes)
TCP established hash table entries: 8192 (order: 6, 294912 bytes)
TCP bind hash table entries: 8192 (order: 5, 229376 bytes)
TCP: Hash tables configured (established 8192 bind 8192)
TCP reno registered
io scheduler noop registered (default)
Boot video device is 0000:00:02.0
Real Time Clock Driver v1.12ac
Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing disabled
serial8250.0: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
serial8250.0: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
Intel(R) PRO/1000 Network Driver - version 7.3.20-k2
Copyright (c) 1999-2006 Intel Corporation.
e1000: 0000:01:02.0: e1000_probe: (PCI:33MHz:32-bit) 00:0b:ab:14:32:31
e1000: eth0: e1000_probe: Intel(R) PRO/1000 Network Connection
e1000: 0000:01:03.0: e1000_probe: (PCI:33MHz:32-bit) 00:0b:ab:14:32:32
e1000: eth1: e1000_probe: Intel(R) PRO/1000 Network Connection
e1000: 0000:01:04.0: e1000_probe: (PCI:33MHz:32-bit) 00:0b:ab:14:32:33
e1000: eth2: e1000_probe: Intel(R) PRO/1000 Network Connection
e1000: 0000:01:05.0: e1000_probe: (PCI:33MHz:32-bit) 00:0b:ab:14:32:34
e1000: eth3: e1000_probe: Intel(R) PRO/1000 Network Connection
Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
ICH4: IDE controller at PCI slot 0000:00:1f.1
ICH4: chipset revision 2
ICH4: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0xf000-0xf007, BIOS settings: hda:pio, hdb:pio
ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdc:pio, hdd:pio
Probing IDE interface ide0...
Probing IDE interface ide1...
hdc: PQI IDE DiskOnModule, ATA DISK drive
hdc: set_drive_speed_status: status=0x51 { DriveReady SeekComplete Error }
hdc: set_drive_speed_status: error=0x04 { DriveStatusError }
ide1 at 0x170-0x177,0x376 on irq 15
hdc: max request size: 128KiB
hdc: 256000 sectors (131 MB) w/1KiB Cache, CHS=500/16/32
hdc: hdc1 hdc2 hdc3 hdc4
TCP cubic registered
NET: Registered protocol family 1
NET: Registered protocol family 17
802.1Q VLAN Support v1.8 Ben Greear <greearb@candelatech.com>
All bugs added by David S. Miller <davem@redhat.com>
Using IPI Shortcut mode
VFS: Mounted root (ext2 filesystem) readonly.
Freeing unused kernel memory: 128k freed
e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full Duplex, Flow Control: RX/TX
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:06 High resolution timers on ACPI-less kernel John Sigler
@ 2007-10-09 9:15 ` Alessio Igor Bogani
2007-10-09 9:28 ` John Sigler
2007-10-09 9:20 ` John Sigler
2007-10-09 9:22 ` Thomas Gleixner
2 siblings, 1 reply; 8+ messages in thread
From: Alessio Igor Bogani @ 2007-10-09 9:15 UTC (permalink / raw)
To: John Sigler; +Cc: linux-rt-users, linux-acpi, Thomas Gleixner
Hi John,
On Tue, 2007-10-09 at 11:06 +0200, John Sigler wrote:
[...]
> I enabled high resolution timer support and disabled ACPI support.
[...]
http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html
Ciao,
Alessio
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:06 High resolution timers on ACPI-less kernel John Sigler
2007-10-09 9:15 ` Alessio Igor Bogani
@ 2007-10-09 9:20 ` John Sigler
2007-10-09 9:22 ` Thomas Gleixner
2 siblings, 0 replies; 8+ messages in thread
From: John Sigler @ 2007-10-09 9:20 UTC (permalink / raw)
To: linux-rt-users; +Cc: linux-acpi, Thomas Gleixner
John Sigler wrote:
> I'm using a -rt kernel with high resolution timer support.
> http://rt.wiki.kernel.org/index.php/Main_Page
> Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT
> RT Tue Oct 9 10:02:45 CEST 2007
>
> I enabled high resolution timer support and disabled ACPI support.
>
> CONFIG_TICK_ONESHOT=y
> # CONFIG_NO_HZ is not set
> CONFIG_HIGH_RES_TIMERS=y
> CONFIG_GENERIC_CLOCKEVENTS_BUILD=y
> # CONFIG_SMP is not set
> ...
> CONFIG_PREEMPT_RT=y
> CONFIG_PREEMPT=y
> CONFIG_PREEMPT_SOFTIRQS=y
> CONFIG_PREEMPT_HARDIRQS=y
> CONFIG_PREEMPT_BKL=y
> # CONFIG_CLASSIC_RCU is not set
> CONFIG_PREEMPT_RCU=y
> # CONFIG_RCU_TRACE is not set
> CONFIG_X86_UP_APIC=y
> CONFIG_X86_UP_IOAPIC=y
> CONFIG_X86_LOCAL_APIC=y
> CONFIG_X86_IO_APIC=y
> ...
> CONFIG_MTRR=y
> CONFIG_REGPARM=y
> # CONFIG_SECCOMP is not set
> CONFIG_HZ_100=y
> # CONFIG_HZ_250 is not set
> # CONFIG_HZ_300 is not set
> # CONFIG_HZ_1000 is not set
> CONFIG_HZ=100
>
> High resolution timers do not work in this configuration.
>
> Any idea why?
>
> # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> tsc pit jiffies
>
> # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> tsc
>
> My timestamp counter is good. Why do I need ACPI for hrt?
I noticed something strange about IRQ0.
It keeps firing even after the system has booted.
# cat /proc/interrupts ; sleep 10 ; cat /proc/interrupts
CPU0
0: 312530 IO-APIC-edge timer
2: 0 XT-PIC-XT cascade
4: 73 IO-APIC-edge serial
8: 1 IO-APIC-edge rtc
15: 16085 IO-APIC-edge ide1
16: 3302 IO-APIC-fasteoi eth0
17: 1560 IO-APIC-fasteoi eth1
18: 1560 IO-APIC-fasteoi eth2
19: 1560 IO-APIC-fasteoi eth3
NMI: 0
LOC: 312489
ERR: 0
MIS: 0
CPU0
0: 313532 IO-APIC-edge timer
2: 0 XT-PIC-XT cascade
4: 73 IO-APIC-edge serial
8: 1 IO-APIC-edge rtc
15: 16109 IO-APIC-edge ide1
16: 3309 IO-APIC-fasteoi eth0
17: 1565 IO-APIC-fasteoi eth1
18: 1565 IO-APIC-fasteoi eth2
19: 1565 IO-APIC-fasteoi eth3
NMI: 0
LOC: 313492
ERR: 0
MIS: 0
IRQ0 is still firing. (1002 times in 10 s = 100 Hz)
When high resolution timers work, the IRQ0 counter stops incrementing
after the system has booted. (When the system switches from the PIT to
the APIC timer AFAIU.) The APIC timer (is that what LOC counts?) also
fired 1003 times in 10 s = 100 Hz.
Is it normal that both the PIT and the APIC timer keep firing?
Regards.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:06 High resolution timers on ACPI-less kernel John Sigler
2007-10-09 9:15 ` Alessio Igor Bogani
2007-10-09 9:20 ` John Sigler
@ 2007-10-09 9:22 ` Thomas Gleixner
2007-10-09 9:39 ` John Sigler
2 siblings, 1 reply; 8+ messages in thread
From: Thomas Gleixner @ 2007-10-09 9:22 UTC (permalink / raw)
To: John Sigler; +Cc: linux-rt-users, linux-acpi
On Tue, 9 Oct 2007, John Sigler wrote:
> Hello everyone,
>
> I'm using a -rt kernel with high resolution timer support.
> http://rt.wiki.kernel.org/index.php/Main_Page
> Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT RT Tue
> Oct 9 10:02:45 CEST 2007
>
> I enabled high resolution timer support and disabled ACPI support.
> ...
> High resolution timers do not work in this configuration.
Correct
> Any idea why?
Yes
> # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> tsc pit jiffies
>
> # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
> tsc
>
> My timestamp counter is good. Why do I need ACPI for hrt?
We do not trust TSC at all. Never ever.
The kernel refuses to switch to high resolution mode, when there is no
reliable backup clock source available. ACPI enables the acpi_pm
timer, which is a trusted clock source and is used by the kernel to
verify the correctness of the TSC. You might try to enable HPET.
tglx
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:15 ` Alessio Igor Bogani
@ 2007-10-09 9:28 ` John Sigler
2007-10-09 9:34 ` Thomas Gleixner
0 siblings, 1 reply; 8+ messages in thread
From: John Sigler @ 2007-10-09 9:28 UTC (permalink / raw)
To: Alessio Igor Bogani; +Cc: linux-rt-users, linux-acpi, Thomas Gleixner
Alessio Igor Bogani wrote:
> On Tue, 2007-10-09 at 11:06 +0200, John Sigler wrote:
> [...]
>> I enabled high resolution timer support and disabled ACPI support.
> [...]
>
> http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html
There are other clock sources on my system.
The timestamp counter is reliable (as far as I can tell).
The LAPIC timer is reliable.
(I've just disabled the PM timer.)
# cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc pit jiffies
# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc
# cat /proc/timer_list
Timer List Version: v0.3
HRTIMER_MAX_CLOCK_BASES: 2
now at 3787164271418 nsecs
cpu: 0
clock 0:
.index: 0
.resolution: 10000000 nsecs
.get_time: ktime_get_real
.offset: 0 nsecs
active timers:
clock 1:
.index: 1
.resolution: 10000000 nsecs
.get_time: ktime_get
.offset: 0 nsecs
active timers:
#0: <cf22bec0>, it_real_fn, S:01
# expires at 3789432883979 nsecs [in 2268612561 nsecs]
.expires_next : 9223372036854775807 nsecs
.hres_active : 0
.nr_events : 0
.nohz_mode : 0
.idle_tick : 0 nsecs
.tick_stopped : 0
.idle_jiffies : 0
.idle_calls : 0
.idle_sleeps : 0
.idle_entrytime : 0 nsecs
.idle_sleeptime : 0 nsecs
.last_jiffies : 0
.next_jiffies : 0
.idle_expires : 0 nsecs
jiffies: 348693
Tick Device: mode: 0
Clock Event Device: pit
max_delta_ns: 27461866
min_delta_ns: 12571
mult: 5124677
shift: 32
mode: 1
next_event: 0 nsecs
set_next_event: pit_next_event
set_mode: init_pit_timer
event_handler: clockevents_handle_noop
tick_broadcast_mask: 00000000
tick_broadcast_oneshot_mask: 00000000
Tick Device: mode: 0
Clock Event Device: lapic
max_delta_ns: 1006581321
min_delta_ns: 1799
mult: 35793226
shift: 32
mode: 2
next_event: 0 nsecs
set_next_event: lapic_next_event
set_mode: lapic_timer_setup
event_handler: tick_handle_periodic
Regards.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:28 ` John Sigler
@ 2007-10-09 9:34 ` Thomas Gleixner
2007-10-09 10:35 ` John Sigler
0 siblings, 1 reply; 8+ messages in thread
From: Thomas Gleixner @ 2007-10-09 9:34 UTC (permalink / raw)
To: John Sigler; +Cc: Alessio Igor Bogani, linux-rt-users, linux-acpi
On Tue, 9 Oct 2007, John Sigler wrote:
> Alessio Igor Bogani wrote:
> > On Tue, 2007-10-09 at 11:06 +0200, John Sigler wrote:
> > [...]
> > > I enabled high resolution timer support and disabled ACPI support.
> > [...]
> >
> > http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html
>
> There are other clock sources on my system.
> The timestamp counter is reliable (as far as I can tell).
See previous mail.
> The LAPIC timer is reliable.
LAPIC timer is a clock event device, not a clock source. It can be
used to program the next event, but not to read the time.
> (I've just disabled the PM timer.)
Yup, which in turn disables highres.
tglx
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:22 ` Thomas Gleixner
@ 2007-10-09 9:39 ` John Sigler
0 siblings, 0 replies; 8+ messages in thread
From: John Sigler @ 2007-10-09 9:39 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-rt-users, linux-acpi
Thomas Gleixner wrote:
> On Tue, 9 Oct 2007, John Sigler wrote:
>
>> I'm using a -rt kernel with high resolution timer support.
>> http://rt.wiki.kernel.org/index.php/Main_Page
>> Linux version 2.6.22.1-rt9 (root@venus) (gcc version 3.4.6) #1 PREEMPT RT Tue
>> Oct 9 10:02:45 CEST 2007
>>
>> I enabled high resolution timer support and disabled ACPI support.
>> ...
>> High resolution timers do not work in this configuration.
>
> Correct
>
>> Any idea why?
>
> Yes
>
>> # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
>> tsc pit jiffies
>>
>> # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
>> tsc
>>
>> My timestamp counter is good. Why do I need ACPI for hrt?
>
> We do not trust TSC at all. Never ever.
>
> The kernel refuses to switch to high resolution mode, when there is no
> reliable backup clock source available. ACPI enables the acpi_pm
> timer, which is a trusted clock source and is used by the kernel to
> verify the correctness of the TSC. You might try to enable HPET.
OK. I seem to remember that you had a patch to enable HPET on ICH4?
Is it still available somewhere?
Regards.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: High resolution timers on ACPI-less kernel
2007-10-09 9:34 ` Thomas Gleixner
@ 2007-10-09 10:35 ` John Sigler
0 siblings, 0 replies; 8+ messages in thread
From: John Sigler @ 2007-10-09 10:35 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-rt-users, linux-acpi
Thomas Gleixner wrote:
> On Tue, 9 Oct 2007, John Sigler wrote:
>> Alessio Igor Bogani wrote:
>>> On Tue, 2007-10-09 at 11:06 +0200, John Sigler wrote:
>>>
>>>> I enabled high resolution timer support and disabled ACPI support.
>>>
>>> http://www.mail-archive.com/linux-rt-users@vger.kernel.org/msg00375.html
>>
>> There are other clock sources on my system.
>> The timestamp counter is reliable (as far as I can tell).
>
> See previous mail.
>
>> The LAPIC timer is reliable.
>
> LAPIC timer is a clock event device, not a clock source. It can be
> used to program the next event, but not to read the time.
>
>> (I've just disabled the PM timer.)
>
> Yup, which in turn disables highres.
OK. I have two more questions.
Can the kernel verify the correctness of the TSC with the PIT?
When I enable the ACPI PM timer, the kernel tells me:
* The chipset may have PM-Timer Bug. Due to workarounds for a bug,
* this clock source is slow. If you are sure your timer does not have
* this bug, please use "acpi_pm_good" to disable the workaround
How can I tell whether my PM timer has this bug or not?
(Specific revision? Test app?)
Regards.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2007-10-09 10:35 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2007-10-09 9:06 High resolution timers on ACPI-less kernel John Sigler
2007-10-09 9:15 ` Alessio Igor Bogani
2007-10-09 9:28 ` John Sigler
2007-10-09 9:34 ` Thomas Gleixner
2007-10-09 10:35 ` John Sigler
2007-10-09 9:20 ` John Sigler
2007-10-09 9:22 ` Thomas Gleixner
2007-10-09 9:39 ` John Sigler
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